A user can provide user input to a computing device using a user input object, such as, for example, one or more fingers, a stylus operated by the user, or other user input objects. In particular, in one example, a user can use a user input object to touch a touch-sensitive display screen or other touch-sensitive component. The interaction of the user input object with the touch-sensitive display screen enables the user to provide user input to the computing device.
However, in certain existing computing devices, a touch event detected by a touch-sensitive display screen must go through a significantly large processing stack before the result of the touch event is displayed on the screen. For example, a touch input processing stack can include a combination of firmware, kernel, rendering, and vertical synchronization (V-Sync) for a liquid crystal display (LCD) screen. The processing stack may also include the software processing done by respective programs which consume the touch input.
The size and complexity of the processing stack introduces the issue of “touch latency,” in which a delay occurs between when the touch event occurs and when the device appears to respond to the touch event. Touch latency is a significant challenge that impacts device performance and user satisfaction. In particular, touch latency is a performance parameter that is highly visible to users and significantly impacts the user experience, typically in a negative way.
While some touch latency could be reduced with better software scheduling, there is a minimum amount of time for a touch event to be processed and then arrive at the screen no matter how well the processing stack has been organized.